f/#180
Added API for sessions store to Redis Api and short unit test

lib/sessions_store.py
test/lib/__init__.py
test/lib/sessions_store.py
Time is now "snapped" at 10 ms before adding it to redis.
AmILabPDU is a new pdu that implements a add_to_session_store method for adding some measurement to redis and also notifying the TrajectoriesPDU about it
Merge pull request #191 from ami-lab/f/#180-redis-api

F/#180 redis api